1. The Field of the Invention
The present invention relates to systems for applying inflation and deflation pressures to a catheter assembly. More particularly, the present invention relates to a system whereby a balloon of a dilation balloon catheter may be selectively and alternatingly inflated and deflated by the operation of an inflation syringe and a vacuum source, respectively.
2. Relevant Technology
In recent years, dilation balloon catheters have become increasingly useful in various medical procedures. For example, dilation balloon catheters have been used to reduce the intrusiveness of medical procedures in various fields of medicine, such as urology, gynecology, cardiology, and the like. Particularly in the treatment of coronary artery disease, the use of dilation balloon catheters and their associated fluid pressurization systems has become widespread.
Coronary artery disease is the narrowing of the arteries that feed oxygen-rich blood to the heart through the buildup of atherosclerotic plaque on the inner walls of the arteries. The heart needs adequate amounts of oxygen to continually and efficiently pump blood throughout the body. When arteries leading to the heart become narrowed and constricted due to coronary artery disease, several problems can develop. A person with coronary artery disease can experience angina, which is characterized by chest pain or pressure that radiates to the arm or jaw and is caused by a lack of oxygen-rich blood to the heart muscle. If untreated, coronary artery disease can lead to or contribute to heart failure and death.
In recent years, coronary angioplasty has become a common and accepted alternative to the vastly more intrusive coronary bypass surgery. Coronary bypass surgery involves surgical access to the heart, placing the patient on an extracorporeal blood oxygenation system so that the heart can be stopped for surgery, and then surgically attaching one or more passageways by which blood can bypass a clogged coronary artery, all under general anesthesia. Coronary angioplasty, which can be performed using a local anesthetic, involves running a dilation balloon catheter (a catheter having an inflatable balloon near the distal end) to a constricted region, or a stenosis, in the diseased artery and then inflating the balloon in order to radially compress atherosclerotic plaque within the artery, thereby obtaining increased blood flow to the heart. Compared to coronary bypass surgery, coronary angioplasty is less intrusive and traumatic, typically involves less risk to the patient, and significantly reduces the patient's discomfort and recovery time.
Dilation balloons are typically inflated using a pressure-generating device that forces pressurized inflation fluid through the lumen of the catheter to the balloon. Examples of pressure-generating devices include syringes and devices having an inflation wire slidably disposed in a lumen of the catheter. The inflation pressure and the duration of inflation of the dilation balloon are often monitored and displayed using appropriate electronic or mechanical sensors and display units so that the operating physician may conduct the coronary angioplasty procedure at the desired intensity and duration.
In addition to the feedback provided by the sensors that detect the pressure and duration of the inflation, some pressure-generating devices that include a relatively small-diameter inflation wire can give an experienced physician tactile feedback relating to the progress of the operation. The tactile feedback can relate to, for example, the progress of the plaque-compression procedure as the dilation balloon is inflated.
Conventional pressure-generating devices that allow tactile feedback suffer from several shortcomings. For example, such pressure-generating devices are conventionally integrally connected to a dilation balloon catheter. This prevents the pressure-generating devices from being interchangeably used with other catheter types. Additionally, the electronic sensors and display units are also integrally attached to such pressure-generating devices, with the result that the sensors and display units must be disposed after one use. Consequently, the cost of treatment using such pressure-generating devices includes the cost of relatively expensive sensors that are used only once. Using an inflation wire is also generally incompatible with the syringe model of inflating dilation balloons.
Pressure-generating devices that allow tactile feedback also have not been compatible with procedures involving the positioning of a stent, which is a support member such as a cylindrical wire coil, in a treated artery at the site of an angioplasty procedure. In a majority of coronary angioplasty procedures, stents are disposed within the treated arteries to prevent the arteries from radially collapsing, which is a common side effect of coronary angioplasty in the absence of stents. A stent is ordinarily applied to a patient by placing the stent on a dilation balloon and advancing the balloon to the desired location. The balloon is inflated in order to compress and position the stent against the interior wall of the artery. The stent is released from the balloon by generating a negative, or deflation, pressure within the dilation balloon. Deflation of the balloon allows the balloon to be withdrawn, while leaving the stent in the desired position within the patient. However, conventional pressure-generating devices that provide tactile feedback have not been capable of generating the negative pressure needed to be compatible with stent placement.
In view of the foregoing, there exists a need in the art for improved pressure-generating devices that can adequately inflate and deflate dilation balloons. There is also a need in the art for pressure-generating devices that provide tactile feedback to the operating physician while being compatible with stent placement procedures.